You have 15 users but you want a 48-port switch? How many ports are you currently using between the two 24-port switches?
The bigger picture in the end is connecting with the various different businesses using different domains, which is under 300 users possibly.
I don't understand this part. What do you mean by this?
I do believe we probably are going to want to be able to do some video conferencing and skype across on the locations, although each location is unique.
How do you currently connect locations together? Does this site already have a proper router?
Well I just started this position this week, out of both 24 port switches only about half of the lights are on, but there are cables plugged into all of the ports except about 8 ports. I know they are going to add some more new hires fairly soon.
This is unique in that there are multiple different types of businesses under one business. None of them are connected together.
I am not sure if it has a proper router. I believe there is a 5505.
The first thing you need to clarify is how many users are you going to plug into that switches.Then you have to consider your basic network infrastructure. Will this network support more people in the future?
I will say you have to determine the network needs of the users: Power Over Ethernet, QoS, Voice & Video, etc.
What will be the role of that switch on the network? It will be a core L3, or an access L2? considering this you will choose the IOS license according to your needs.
Where to buy? The safest place is to go with an authorized partner reseller.
You can find one on the link below according to the country you are living .